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Add testing of bitflips in packet headers
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A new type of noise is introduced in the noisy dgram bio
filter.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from #22267)
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@t8m
t8m committed Oct 6, 2023
1 parent 7ae3158 commit 6dfc57f
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Showing 2 changed files with 69 additions and 22 deletions.
63 changes: 55 additions & 8 deletions test/helpers/noisydgrambio.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,8 @@ static int noisy_dgram_sendmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
#define NOISE_TYPE_DROP 0
#define NOISE_TYPE_DUPLICATE 1
#define NOISE_TYPE_DELAY 2
#define NUM_NOISE_TYPES 3
#define NOISE_TYPE_BITFLIPS 3
#define NUM_NOISE_TYPES 4

/*
* When a duplicate occurs we reinject the new datagram after up to
Expand All @@ -89,10 +90,13 @@ static int noisy_dgram_sendmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
*/
#define MAX_DGRAM_REINJECT 4

static void get_noise(uint64_t *reinject, int *should_drop)
static void get_noise(int long_header, uint64_t *reinject, int *should_drop,
uint16_t *flip, size_t *flip_offset)
{
uint32_t type;

*flip = 0;

if (test_random() % NOISE_RATE != 0) {
*reinject = 0;
*should_drop = 0;
Expand All @@ -102,7 +106,7 @@ static void get_noise(uint64_t *reinject, int *should_drop)
type = test_random() % NUM_NOISE_TYPES;

/*
* Of noisy datagrams, 33% drop, 33% duplicate, 33% delay
* Of noisy datagrams, 25% drop, 25% duplicate, 25% delay, 25% flip bits
* A duplicated datagram keeps the current datagram and reinjects a new
* identical one after up to MAX_DGRAM_DELAY datagrams have been sent.
* A delayed datagram is implemented as both a reinject and a drop, i.e. an
Expand All @@ -115,16 +119,50 @@ static void get_noise(uint64_t *reinject, int *should_drop)
* Where a duplicate occurs we reinject the copy of the datagram up to
* MAX_DGRAM_DELAY datagrams later
*/
*reinject = (type == NOISE_TYPE_DROP)
? 0
: (uint64_t)((test_random() % MAX_DGRAM_REINJECT) + 1);
*reinject = (type == NOISE_TYPE_DUPLICATE || type == NOISE_TYPE_DELAY)
? (uint64_t)((test_random() % MAX_DGRAM_REINJECT) + 1)
: 0;

/*
* No point in reinjecting after 1 datagram if the current datagram is also
* dropped (i.e. this is a delay not a duplicate), so we reinject after an
* extra datagram in that case
*/
*reinject += (uint64_t)(*should_drop);
*reinject += type == NOISE_TYPE_DELAY;

/* flip some bits in the header */
if (type == NOISE_TYPE_BITFLIPS) {
/* we flip at most 8 bits of the 16 bit value at once */
*flip = (test_random() % 255 + 1) << (test_random() % 8);
/*
* 25/50 bytes of guesstimated header size (it depends on CID length)
* It does not matter much if it is overestimated.
*/
*flip_offset = test_random() % (25 * (1 + long_header));
}
}

static void flip_bits(unsigned char *msg, size_t msg_len, uint16_t flip,
size_t flip_offset)
{
if (flip == 0)
return;

/* None of these border conditions should happen but check them anyway */
if (msg_len < 2)
return;
if (msg_len < flip_offset + 2)
flip_offset = msg_len - 2;

#ifdef OSSL_NOISY_DGRAM_DEBUG
printf("**Flipping bits in a datagram at offset %u\n",
(unsigned int)flip_offset);
BIO_dump_fp(stdout, msg, msg_len);
printf("\n");
#endif

msg[flip_offset] ^= flip >> 8;
msg[flip_offset + 1] ^= flip & 0xff;
}

static int noisy_dgram_recvmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
Expand Down Expand Up @@ -181,6 +219,8 @@ static int noisy_dgram_recvmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
i++, thismsg++, data->this_dgram++) {
uint64_t reinject;
int should_drop;
uint16_t flip;
size_t flip_offset;

/* If we have a message to reinject then insert it now */
if (data->reinject_dgram > 0
Expand All @@ -205,7 +245,8 @@ static int noisy_dgram_recvmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
data->reinject_dgram = 0;
}

get_noise(&reinject, &should_drop);
get_noise(/* long header */ (((uint8_t *)thismsg->data)[0] & 0x80) != 0,
&reinject, &should_drop, &flip, &flip_offset);
if (data->backoff) {
/*
* We might be asked to back off on introducing too much noise if
Expand All @@ -214,10 +255,16 @@ static int noisy_dgram_recvmmsg(BIO *bio, BIO_MSG *msg, size_t stride,
* that the connection always survives. After that we can resume
* with normal noise
*/
#ifdef OSSL_NOISY_DGRAM_DEBUG
printf("**Back off applied\n");
#endif
should_drop = 0;
flip = 0;
data->backoff = 0;
}

flip_bits(thismsg->data, thismsg->data_len, flip, flip_offset);

/*
* We ignore reinjection if a message is already waiting to be
* reinjected
Expand Down
28 changes: 14 additions & 14 deletions test/quicapitest.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1439,11 +1439,11 @@ static int test_noisy_dgram(int idx)
qtest_add_time(1);

/*
* Send data from the server to the client. Some datagrams may get lost,
* dropped or re-ordered. We repeat 10 times to ensure we are sending
* enough datagrams for problems to be noticed.
*/
for (i = 0; i < 10; i++) {
* Send data from the server to the client. Some datagrams may get
* lost, modified, dropped or re-ordered. We repeat 20 times to ensure
* we are sending enough datagrams for problems to be noticed.
*/
for (i = 0; i < 20; i++) {
if (!TEST_true(ossl_quic_tserver_write(qtserv, sid,
(unsigned char *)msg, msglen,
&written))
Expand All @@ -1453,10 +1453,10 @@ static int test_noisy_dgram(int idx)
qtest_add_time(1);

/*
* Since the underlying BIO is now noisy we may get failures that
* need to be retried - so we use unreliable_client_read() to handle
* that
*/
* Since the underlying BIO is now noisy we may get failures that
* need to be retried - so we use unreliable_client_read() to
* handle that
*/
if (!TEST_true(unreliable_client_read(clientquic, &stream[j], buf,
sizeof(buf), &readbytes,
qtserv))
Expand All @@ -1465,7 +1465,7 @@ static int test_noisy_dgram(int idx)
}

/* Send data from the client to the server */
for (i = 0; i < 10; i++) {
for (i = 0; i < 20; i++) {
if (!TEST_true(SSL_write_ex(stream[j], (unsigned char *)msg,
msglen, &written))
|| !TEST_size_t_eq(msglen, written))
Expand All @@ -1475,10 +1475,10 @@ static int test_noisy_dgram(int idx)
qtest_add_time(1);

/*
* Since the underlying BIO is now noisy we may get failures that
* need to be retried - so we use unreliable_server_read() to handle
* that
*/
* Since the underlying BIO is now noisy we may get failures that
* need to be retried - so we use unreliable_server_read() to
* handle that
*/
if (!TEST_true(unreliable_server_read(qtserv, sid, buf, sizeof(buf),
&readbytes, clientquic))
|| !TEST_mem_eq(msg, msglen, buf, readbytes))
Expand Down

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